The present disclosure relates to emissive materials, and more particularly, to emissive materials for space and/or vacuum applications.
Electric power lines, mammal bodies, vehicle engines, and aircrafts are examples of living organisms and objects that produce and retain heat. These objects and bodies are visible in the infrared (IR) wavelengths of light against objects in the background because hot bodies strongly radiate IR waves. The objects in the background are relatively cooler objects.
Missile guidance systems use IR seekers to track and follow targets by locating the IR emissions from the targets. IR seekers can be IR temperature sensors and can be calibrated to identify object temperatures based on the object color in an IR photograph. IR sensors are also used in space based systems. Cryogenic vacuum chambers simulate space conditions. Cryogenic blackbody cores are used to characterize or calibrate IR sensors.
Teaching, characterizing, and calibrating an IR sensor or seeker to record specific colors corresponding to specific temperatures involve several steps. Initially, a cryogenic blackbody core, an IR source, is heated. Then a temperature sensor reads the temperature of the heated blackbody core. An IR camera takes a photograph of the heated blackbody core and displays colors according to the temperature of the blackbody. The IR seeker memory is programmed to store a color-temperature association between the measured temperature and the color of the object on the IR photograph. The IR seeker is programmed to know that the color displayed by the blackbody core corresponds to the temperature read by the temperature sensor.
Surface materials used in cryogenic vacuum (space) rated IR sources and blackbody cores must be highly emissive (low reflectance) and not susceptible to vaporization induced mass loss. High emissivity and vaporization-induced mass loss properties also must be sustainable over the temperature and spectral range that the IR source operates. Further, in some instances, the surface material must substantially bond to other materials. However, currently available coatings in cryogenic vacuum rated IR sources, e.g., oxide coatings such as ATK's vacuum rated blackbody coating, a proprietary coating of stainless steel oxide, have substantially non-flat spectral reflectivity curves and can degrade under high thermal operations.